Decolorization method for dyed fiber cloth

ABSTRACT

A decolorization method for a dyed fiber cloth is provided. The decolorization method for the dyed fiber cloth includes steps of: providing a fiber cloth attached with a dye, extracting the dye attached on the fiber cloth by an extractant, and applying a microwave to evaporate the extractant so as to obtain a dried and decolored fiber cloth.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 110106481, filed on Feb. 24, 2021. The entire content of the above identified application is incorporated herein by reference.

Some references, which may include patents, patent applications and various publications, may be cited and discussed in the description of this disclosure. The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to the disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a decolorization method for a dyed fiber cloth, and more particularly to a decolorization method for the dyed fiber cloth which can effectively recover the extractant.

BACKGROUND OF THE DISCLOSURE

As environmental protection consciousness gains traction, how to recycle and reuse industrial and household waste has become an important issue and business opportunity nowadays. Among various recyclable products, fiber cloth is of much importance. In a recycling process for the fiber cloth, dye attached on the fiber cloth should be completely removed before a next purifying step of the fiber cloth can be implemented.

In order to remove the dye attached on the fiber cloth, an extractant is generally used to extract the dye. Methods of enhancing an extraction effect of the extractant are provided in the conventional technology, such as using a specific extractant, or performing specific extracting steps in cooperation with use of the extractant.

Regarding the whole decolorization process, while the extraction effect of the extractant to the dye is certainly important, increasing a recovery rate of the extractant and reducing an amount of extractant that is discharged is also vital for the sake of environmental protection. If the extractant is arbitrarily discharged, the surrounding environment would be polluted, thus contradicting an original intention of environmental sustainability. Therefore, the present disclosure provides an improved method that aims to enhance the recovery rate of the extractant, such that an impact to the environment can be decreased, and usage of the extractant in the decolorization process can be reduced.

In a conventional decolorization method, the fiber cloth is dried by hot air or vacuum drying after being extracted. The extractant can be recovered by means of collecting a heated gas or collecting a gas that is evacuated. Whether drying by hot air or by vacuum drying, the extractant is taken away from the fiber cloth via a gaseous medium (the heated gas and the evacuated gas) to dry the fiber cloth. However, since the extractant is easily lost during drying, the recovery rate of the extractant is difficult to be enhanced. Generally, the recovery rate of the extractant in the conventional decolorization method is not higher than 80%.

SUMMARY OF THE DISCLOSURE

In response to the above-referenced technical inadequacy, the present disclosure provides a decolorization method for a dyed fiber cloth.

In one aspect, the present disclosure provides a decolorization method for a dyed fiber cloth. The method includes the following steps: providing a fiber cloth attached with a dye, extracting the dye attached on the fiber cloth by an extractant, and applying a microwave to evaporate the extractant so as to obtain a dried and decolored fiber cloth.

In some embodiments of the present disclosure, the fiber cloth is extracted at a temperature ranging from 70° C. to 130° C.

In some embodiments of the present disclosure, a part of the extractant is separated by filtration before applying the microwave.

In some embodiments of the present disclosure, after the filtration, based on a total weight of the fiber cloth and the extractant remaining on the fiber cloth being 100 wt %, a residue of the extractant remaining on the fiber cloth ranges from 5 wt % to 70 wt %.

In some embodiments of the present disclosure, after applying the microwave, based on a total weight of the fiber cloth and the extractant remaining on the fiber cloth being 100 wt %, a residue of the extractant remaining on the fiber cloth ranges from 0 wt % to 5 wt %.

In some embodiments of the present disclosure, the extractant is condensed and collected, and a recovery rate of the extractant is higher than or equal to 90%.

In some embodiments of the present disclosure, a weight ratio of the extractant to the fiber cloth ranges from 10 to 30.

In some embodiments of the present disclosure, when applying the microwave, a direction of heat transfer of the extractant and a direction of mass transfer of the extractant are a same direction.

In some embodiments of the present disclosure, after applying the microwave, a temperature of the fiber cloth is higher than a boiling point of the extractant.

In some embodiments of the present disclosure, the dye attached on the fiber cloth is extracted from one to six times by the extractant.

Therefore, by virtue of “applying the microwave to evaporate the extractant”, the decolorization method of the present disclosure can reduce a loss of the extractant and enhance the recovery rate of the extractant.

These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments may be better understood by reference to the following description and the accompanying drawings, in which:

FIG. 1 is a flowchart of a decolorization method for a dyed fiber cloth of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a”, “an”, and “the” includes plural reference, and the meaning of “in” includes “in” and “on”. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.

The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first”, “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.

In order to improve on the problem of low recovery rate of an extractant, the present disclosure provides a decolorization method for a dyed fiber cloth. The decolorization method for the dyed fiber cloth includes three parts: providing a fiber cloth attached with a dye (step S1), extracting the dye attached on the fiber cloth (step S2), and drying the fiber cloth (steps S3 and S4).

It should be noted that, in the part of drying the fiber cloth, energy (such as a microwave) is applied to the fiber cloth, so as to directly heat the fiber cloth for drying rather than indirectly heat the fiber cloth via other mediums (such as a heated gas).

When a temperature of the fiber cloth is higher than a boiling point of the extractant, the extractant attached or remained on the fiber cloth is evaporated. Therefore, the evaporated extractant can be condensed and collected so that the extractant is recovered. Since no gas medium is used to heat the fiber cloth in the present disclosure, the evaporated extractant is not diluted by the gas medium so that the extractant having a high concentration can be condensed and collected. A loss of the extractant can be decreased.

Referring to FIG. 1, the decolorization method for the dyed fiber cloth of the present disclosure includes steps of: providing the fiber cloth attached with the dye (step S1), extracting the dye attached on the fiber cloth (step S2), separating a part of the extractant by filtration (step S3), and applying a microwave to the fiber cloth in a closed container to evaporate another part of extractant so as to obtain a dried and decolored fiber cloth (step S4). The decolorization method for the dyed fiber cloth of the present disclosure can not only decolor the dyed fiber cloth but also recover more than 90% of the extractant, thereby preventing the extractant from polluting environment.

In step S1, the dyed fiber cloth is the fiber cloth attached with the dye.

The fiber cloth can be a fiber cloth formed from a polyester material. The polyester material can be polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), or polyarylate (PAR). In addition, the polyester material can include other components, such as cotton or nylon, but the present disclosure is not limited thereto.

In step S2, the dye attached on the fiber cloth can be extracted by using the extractant. If the dye can be extracted by the extractant, then the present disclosure is not limited to various ways of mixing the extractant and the fiber cloth, and the various ways are all within a scope of the present disclosure.

In some embodiments, the extractant can directly contact the fiber cloth in a liquid state to extract the dye. Specifically, the extractant and the fiber cloth can be put in a decolorization tank and then be continuously mixed and stirred, thus the extractant can continuously contact the fiber cloth to extract the dye. In this way, a concentration of the dye in the extractant may increase over time. When the concentration of the dye in the extractant reaches a saturated concentration, an extraction effect of the extractant may be reduced and the fiber cloth may be redyed. Therefore, a fresh extractant is required to be supplied during extraction.

In other embodiments, the extractant can contact the fiber cloth in a gas state to extract the dye. Specifically, the extractant is heated to obtain an evaporated extractant, and then the evaporated extractant contacts the fiber cloth to extract the dye. In this way, the fiber cloth contacts the evaporated extractant having a high purity. Therefore, the extraction effect of the extractant will not be restricted to the concentration of the dye in the extractant, and the fiber cloth will not be redyed.

Further, in the present disclosure, the dye is extracted at a temperature ranging from 70° C. to 130° C. so that the extraction effect of the extractant can be enhanced. Preferably, the dye is extracted at a temperature ranging from 110° C. to 130° C. The fiber cloth can be extracted from one to six times so as to completely decolor the fiber cloth. The fiber cloth having an L value of higher than 75 can be obtained.

In some embodiments, a weight ratio of the extractant to the fiber cloth ranges from 10 to 30. When an amount of the extractant is few, extraction duration should be prolonged and the fresh extractant should be supplied more often. When the amount of the extractant is excessive, large amounts of the extractant need to be treated after decolorization and this leads to a high processing cost.

In some embodiments, the extractant can be selected according to materials of the fiber cloth and types of the dye. For example, the extractant can be selected from the group consisting of: ethylene glycol monomethyl ether (EM, boiling point: 124° C.), diethylene glycol monomethyl ether (DEM, boiling point: 194° C.), triethylene glycol monomethyl ether (TEM, boiling point: 122° C.), ethylene glycol monoethyl ether (EE, boiling point: 135.6° C.), diethylene glycol monoethyl ether (DE, boiling point: 201.9° C.), ethylene glycol monobutyl ether (EB, boiling point: 171° C.), ethylene glycol propyl ether (EP, boiling point: 151.3° C.), propylene glycol monomethyl ether (PM, boiling point: 120° C.), dipropylene glycol monomethyl ether (DPM, boiling point: 190° C.), propylene glycol monoethyl ether (PE, boiling point: 132.8° C.), dipropylene glycol monoethyl ether (DPE, boiling point: 223.5° C.), propylene glycol monobutyl ether (PNB, boiling point: 171.1° C.), dipropylene glycol monobutyl ether (DPNB, boiling point: 222° C.), propylene glycol propyl ether (PP, boiling point: 149° C.), and dipropylene glycol propyl ether (DPP, boiling point: 243° C.). However, the present disclosure is not limited thereto.

Preferably, the extractant can be at least one of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. In a preferable embodiment, the extractant is propylene glycol monomethyl ether that has a better extraction effect.

As for the part of drying the fiber cloth, in the present disclosure, a part of the extractant is separated by filtration (step S3), and another part of the extractant is separated through evaporation by applying the microwave (step S4). Therefore, duration of the overall process can be shortened and the recovery rate of the extractant can be enhanced. It should be noted that step S3 is an optional step, and step S3 can be implemented or omitted according to practical process.

In some embodiments, when the extractant in the liquid state contacts the dye for extraction, the filtration step (step S3) is usually carried out to separate a part of the extractant before applying the microwave (step S4), so that the fiber cloth can be dried quickly and energy consumption can be reduced.

In other embodiments, when the extractant in the gas state contacts the dye and then condenses on the fiber cloth for extraction, the filtration step (step S3) is not necessary to be carried out before applying the microwave (step S4).

In step S3, a part of the extractant is separated from the fiber cloth by filtration. In some embodiments, a filter with a pore size smaller than 1 cm can be used to separate the fiber cloth and the extractant by gravity. In other embodiments, the fiber cloth and the extractant can also be separated by centrifugation. However, the present disclosure is not limited thereto.

After the filtration step (step S3), based on a total weight of the fiber cloth and the extractant remained on the fiber cloth being 100 wt %, a residue of the extractant remained on the fiber cloth ranges from 5 wt % to 70 wt %. Preferably, the residue of the extractant remaining on the fiber cloth ranges from 5 wt % to 60 wt %.

In step S4, a microwave is applied into a closed container to evaporate another part of the extractant so that a dried and decolored fiber cloth can be obtained. After the drying step (step S4), based on a total weight of the fiber cloth and the extractant remained on the fiber cloth being 100 wt %, a residue of the extractant remaining on the fiber cloth ranges from 0 wt % to 5 wt %.

In the present disclosure, the step of applying a microwave to heat the fiber cloth and the extractant can not only dry the fiber cloth but also enhance the recovery rate of the extractant.

In the present disclosure, the fiber cloth is heated by applying the microwave without any gas medium. Specifically, when the microwave is absorbed by the fiber cloth, electromagnetic energy is transformed into heat energy. Then, the heat energy is stored in the fiber cloth, and a temperature of the extractant gradually increases. Once the temperature of the extractant reaches the boiling point of the extractant, the extractant evaporates and is separated from the fiber cloth, so that the fiber cloth can be dried.

In the drying step of applying the microwave, no gas medium (such as heated gas) is used to transfer energy, such that energy consumption can be reduced and a drying efficiency can be enhanced.

In the step of condensing and collecting the evaporated extractant, the gas medium is excluded, such that the evaporated extractant is not easily lost when the evaporated extractant is carried by the gas medium. Accordingly, the low recovery rate of the extractant can be improved.

Microscopically, after applying the microwave, the temperature of the extractant is higher than a temperature of the surrounding, therefore, a direction of heat transfer is outward. When the extractant evaporates, a direction of mass transfer of the evaporated extractant is also outward. In other words, as for the extractant, the direction of heat transfer and the direction of mass transfer are a same direction. Accordingly, applying the microwave can accelerate a drying rate and omit the using of the gas medium.

In a conventional method, a heated gas is introduced to dry the fiber cloth. For the extractant, the temperature of the extractant is raised by the heated gas and a direction of heat transfer is inward. When the temperature of the extractant reaches the boiling point of the extractant, the extractant evaporates and a direction of mass transfer is outward. In other words, for the extractant, the direction of heat transfer is opposite to the direction of mass transfer.

In an exemplary example, a power of the microwave ranges from 50 W to 500 W. Preferably, the power of the microwave ranges from 100 W to 400 W. In an exemplary example, duration of applying the microwave ranges from 5 minutes to 30 minutes, but is not limited thereto. Preferably, the duration of applying the microwave ranges from 10 minutes to 30 minutes. The duration of applying the microwave can be adjusted according the power supplied to the microwave.

In an exemplary example, after applying the microwave, the temperature of the fiber cloth is higher than the boiling point of the extractant. Specifically, after applying the microwave, the temperature of the fiber cloth ranges from 130° C. to 160° C. Preferably, after applying the microwave, the temperature of the fiber cloth ranges from 140° C. to 150° C.

Recovery Rate Test

In order to prove that the step of applying the microwave of the present disclosure can enhance the recovery rate of the extractant, Examples 1 to 8 and Comparative Examples 1 to 4 are prepared according to the decolorization method.

Examples 1 to 4

100 g of a PET fiber cloth and 1500 g of propylene glycol monomethyl ether (extractant) are put in a flask and stirred at a temperature of 120° C. for 1 hour to extract the dye attached on the PET fiber cloth. Then, the PET fiber cloth and propylene glycol monomethyl ether are separated from each other by filtration. The extraction step and the filtration step are repeated twice so as to completely remove the dye.

After the filtration step (step S3), the PET fiber cloth is weighed, and the residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant in each of Examples 1 to 4 are listed in Table 1. According to Table 1, the residue of propylene glycol monomethyl ether remained on the PET fiber cloth ranges from 25 g to 150 g. In other words, after the filtration step, based on the total weight of the PET fiber cloth and propylene glycol monomethyl ether remained on the PET fiber cloth being 100 wt %, the residue of the extractant ranges from 20 wt % to 60 wt %.

Subsequently, a microwave of a power of 300 W is applied to maintain a surface temperature of the PET fiber cloth at 145° C. for 20 minutes, so as to evaporate propylene glycol monomethyl ether and dry the PET fiber cloth. The dried and decolored fiber cloth having the L value of higher than 75% can be obtained.

After the drying step (step S4), the PET fiber cloth is weighed, and a residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant after the drying step in each of Examples 1 to 4 are listed in Table 1.

The evaporated propylene glycol monomethyl ether is condensed and collected by a condenser. After being cooled down to a temperature of 25° C., the condensed extractant is weighed, and a loss of the extractant during evaporation or condensation is calculated. The loss of the extractant after the drying step=(the residue of the extractant after the filtration step−the residue of the extractant after the drying step−a condensed amount of the extractant after the drying step). The condensed amount of the extractant after the drying step and the loss of the extractant after the drying step in each of Examples 1 to 4 are listed in Table 1.

In order to prove that applying the microwave can enhance the recovery rate of the extractant, the recovery rate of the extractant is calculated by a formula: (the condensed amount of the extractant after the drying step/the residue of the extractant after the filtration step)×100%. The recovery rate of the extractant in each of Examples 1 to 4 is listed in Table 1.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Net weight of fiber cloth (g) 100 100 100 100 After step Weight of fiber cloth (g) 125 142.9 166.7 250 S3 Residue of extractant (g) 25 42.9 66.7 150 Residue of extractant (wt %) 20 30 40 60 After step Fiber cloth weight (g) 100.2 100.4 101.1 101.5 S4 Residue of extractant (g) 0.2 0.4 1.1 1.5 Residue of extractant (wt %) 0.2 0.4 1.1 1.5 Condensed amount of 24.7 42.3 65.2 148.0 extractant (g) Loss of extractant (g) 0.1 0.2 0.4 0.5 Recovery rate of extractant (%) 98.8 98.6 97.8 98.7

Examples 5 to 8

Examples 5 to 8 are similar to Examples 1 to 4 mentioned previously. The difference is that the surface temperature of the fiber cloth of Examples 5 to 8 in the drying step (step S4) is maintained at 145° C. for 10 minutes.

100 g of a PET fiber cloth and 1500 g of propylene glycol monomethyl ether (extractant) are put in a flask and stirred at a temperature of 120° C. for 1 hour to extract the dye attached on the PET fiber cloth. Then, the PET fiber cloth and propylene glycol monomethyl ether are separated from each other by filtration. The extraction step and the filtration step are repeated twice so as to completely remove the dye.

After the filtration step (step S3), the PET fiber cloth is weighed, and the residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant in each of Examples 5 to 8 are listed in Table 2. According to Table 2, the residue of propylene glycol monomethyl ether remained on the PET fiber cloth ranges from 25 g to 150 g. In other words, after the filtration step, based on the total weight of the PET fiber cloth and propylene glycol monomethyl ether remained on the PET fiber cloth being 100 wt %, the residue of the extractant ranges from 20 wt % to 60 wt %.

Subsequently, a microwave of a power of 300 W is applied to maintain a surface temperature of the PET fiber cloth at 145° C. for 10 minutes, so as to evaporate propylene glycol monomethyl ether and dry the PET fiber cloth. The dried and decolored fiber cloth having the L value of higher than 75% can be obtained.

After the drying step (step S4), the PET fiber cloth is weighed, and a residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant after the drying step in each of Examples 5 to 8 are listed in Table 2.

The evaporated propylene glycol monomethyl ether is condensed and collected by a condenser. After being cooled down to a temperature of 25° C., the condensed extractant is weighed, and a loss of the extractant during evaporation or condensation is calculated. The loss of the extractant after the drying step=(the residue of the extractant after the filtration step−the residue of the extractant after the drying step−a condensed amount of the extractant after the drying step). The condensed amount of the extractant after the drying step and the loss of the extractant after the drying step in each of Examples 5 to 8 are listed in Table 2.

In order to prove that applying the microwave can enhance the recovery rate of the extractant, the recovery rate of the extractant is calculated by a formula: (the condensed amount of the extractant after the drying step/the residue of the extractant after the filtration step)×100%. The recovery rate of the extractant in each of Examples 5 to 8 is listed in Table 2.

TABLE 2 Example 5 Example 6 Example 7 Example 8 Net weight of fiber cloth (g) 100 100 100 100 After step Weight of fiber cloth (g) 125 142.9 166.7 250 S3 Residue of extractant (g) 25 42.9 66.7 150 Residue of extractant (wt %) 20 30 40 60 After step Weight of fiber cloth (g) 100.4 100.8 102.2 103.6 S4 Residue of extractant (g) 0.4 0.8 2.2 3.6 Residue of extractant (wt %) 0.4 0.8 2.2 3.5 Condensed amount of 24.5 42.0 64.1 146.0 extractant (g) Loss of extractant (g) 0.1 0.1 0.4 0.4 Recovery rate of extractant (%) 98.0 97.9 96.1 97.3

Based on results of Table 1 and Table 2, applying the microwave to evaporate the extractant can dramatically decrease the loss of the extractant, thereby increasing the recovery rate of the extractant. Specifically, after the drying step (step S4), the loss of the extractant is lower than 1 g. Preferably, the loss of the extractant is lower than 0.5 g. The recovery rate of the extractant is higher than 90%. Preferably, the recovery rate of the extractant is higher than 95%. More preferably, the recovery rate of the extractant is higher than 96%.

The smaller the residue of the extractant after the filtration step (step S3) is, the smaller the residue of the extractant after the drying step (step S4) is. Specifically, by controlling the residue of the extractant after the filtration step (step S3) ranging from 20 wt % to 60 wt %, the residue of the extractant after the drying step (step S4) can range from 0 wt % to 5 wt %.

Comparative Examples 1 to 4

Comparative Examples 1 to 4 are similar to Examples 1 to 4 mentioned previously. The difference is that the fiber cloth in each of Comparative Examples 1 to 4 is dried by a heated gas, rather than a microwave.

In Comparative Examples 1 to 4, 100 g of a PET fiber cloth and 1500 g of propylene glycol monomethyl ether (extractant) are put in a flask and stirred at a temperature of 120° C. for 1 hour to extract the dye attached on the PET fiber cloth. Then, the PET fiber cloth and propylene glycol monomethyl ether are separated from each other by filtration. The extraction step and the filtration step are repeated twice so as to completely remove the dye.

After the filtration step, the PET fiber cloth is weighed, and the residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant in each of Comparative Examples 1 to 4 are listed in Table 3. After the filtration step, based on the total weight of the PET fiber cloth and propylene glycol monomethyl ether remained on the PET fiber cloth being 100 wt %, the residue of the extractant ranges from 20 wt % to 60 wt %.

Subsequently, the heated gas with a volumetric flow rate of 10 Nm³/min is introduced to maintain a surface temperature of the PET fiber cloth at 145° C. for 20 minutes so as to evaporate propylene glycol monomethyl ether and dry the PET fiber cloth. The dried and decolored fiber cloth having the L value higher than 75% can be obtained.

After the drying step, the PET fiber cloth is weighed, and a residue of the extractant remained on the PET fiber cloth is calculated. The weight of the PET fiber cloth and the residue of the extractant after the drying step in each of Comparative Examples 1 to 4 are listed in Table 3.

The evaporated propylene glycol monomethyl ether is condensed and collected by a condenser. After being cooled down to a temperature of 25° C., the condensed extractant is weighed, and a loss of the extractant during evaporation or condensation is calculated. The loss of the extractant after the drying step=(the residue of the extractant after the filtration step−the residue of the extractant after the drying step−a condensed amount of the extractant after the drying step). The condensed amount of the extractant after the drying step and the loss of the extractant after the drying step in each of Comparative Examples 1 to 4 are listed in Table 3.

In order to prove that applying the microwave can enhance the recovery rate of the extractant, the recovery rate of the extractant is calculated by a formula: (the condensed amount of the extractant after the drying step/the residue of the extractant after the filtration step)×100%. The recovery rate of the extractant in each of Comparative Examples 1 to 4 is listed in Table 3.

TABLE 3 Comparative Example 1 2 3 4 Net weight of fiber cloth (g) 100 100 100 100 After Weight of fiber cloth (g) 125 142.9 166.7 250 step Residue of extractant (g) 25 42.9 66.7 150 S3 Residue of extractant (wt %) 20 30 40 60 After Weight of fiber cloth (g) 100.3 100.5 101.1 101.4 step Residue of extractant (g) 0.3 0.5 1.1 1.4 S4 Residue of extractant (wt %) 0.3 0.5 1.1 1.4 Condensed amount of 20.0 34.8 54.1 128 extractant (g) Loss of extractant (g) 4.7 7.6 11.5 20.6 Recovery rate of extractant (%) 80.0 81.1 81.1 85.3

Based on results in Table 3, introducing the heated gas to evaporate the extractant causes more loss of the extractant, thus the recovery rate of the extractant cannot be enhanced. Specifically, after the drying step, the loss of the extractant ranges from 4 g to 21 g, and the recovery rate of the extractant ranges from 80% to 86%.

Accordingly, based on the results of Tables 1 to 3, applying the microwave to evaporate the extractant to dry the fiber cloth in the present disclosure can reduce the loss of the extractant and enhance the recovery rate of the extractant. Compared to the conventional method that uses heated gas to dry the fiber cloth, the decolorization method of the present disclosure can have a higher recovery rate of the extractant.

Beneficial Effects of the Embodiment

In conclusion, by virtue of “applying the microwave to evaporate the extractant”, the decolorization method of the present disclosure can reduce a loss of the extractant and enhance the recovery rate of the extractant.

Further, by virtue of “separating a part of the extractant by filtration before applying the microwave”, a part of the extractant is separated by filtration, and the decolorization method of the present disclosure can reduce energy consumption of applying the microwave.

Further, by virtue of “the direction of heat transfer and the direction of mass transfer being the same in the step of applying a microwave”, the decolorization method of the present disclosure can reduce the loss of the extractant and enhance the recovery rate of the extractant.

The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope. 

What is claimed is:
 1. A decolorization method for a dyed fiber cloth, comprising: providing a fiber cloth attached with a dye; extracting the dye attached on the fiber cloth by an extractant; and applying a microwave to evaporate the extractant so as to obtain a dried and decolored fiber cloth.
 2. The decolorization method according to claim 1, wherein the fiber cloth is extracted at a temperature ranging from 70° C. to 130° C.
 3. The decolorization method according to claim 1, further comprising separating a part of the extractant by filtration before applying the microwave.
 4. The decolorization method according to claim 3, wherein, after the filtration, based on a total weight of the fiber cloth and the extractant remained on the fiber cloth being 100 wt %, a residue of the extractant remaining on the fiber cloth ranges from 5 wt % to 70 wt %.
 5. The decolorization method according to claim 1, wherein, after applying the microwave, based on a total weight of the fiber cloth and the extractant remained on the fiber cloth being 100 wt %, a residue of the extractant remaining on the fiber cloth ranges from 0 wt % to 5 wt %.
 6. The decolorization method according to claim 1, further comprising condensing and collecting the extractant after applying the microwave, and a recovery rate of the extractant being higher than or equal to 90%.
 7. The decolorization method according to claim 1, wherein a weight ratio of the extractant to the fiber cloth ranges from 10 to
 30. 8. The decolorization method according to claim 1, wherein, when applying the microwave, a direction of heat transfer of the extractant and a direction of mass transfer of the extractant are a same direction.
 9. The decolorization method according to claim 1, wherein, after applying the microwave, a temperature of the fiber cloth is higher than a boiling point of the extractant.
 10. The decolorization method according to claim 1, wherein the dye attached on the fiber cloth is extracted from one to six times by the extractant. 